rthorne at VNET.IBM.COM
rthorne at VNET.IBM.COM
Fri Aug 26 11:02:32 EDT 1994
I have had a couple of requests for my source of the surge surpressor. I'll
post it for everyone.
We went to a local electrical supply house to place the order. Its a GE part.
Tranquell Secondary Arrestor, 9L15FCB001.
The supply house just gave us a call when they came in and the rest is history.
Rich - WB5M - RTHORNE at VNET.IBM.COM
>From John W. Brosnahan" <broz at csn.org Fri Aug 26 16:20:27 1994
From: John W. Brosnahan" <broz at csn.org (John W. Brosnahan)
Date: Fri, 26 Aug 1994 09:20:27 -0600
Subject: Surge Suppression and Torque Guying (and 75 KW transmitters)
Message-ID: <199408261520.AA20115 at teal.csn.org>
A number of the utilities make available a very heavy duty surge protector
for about $130 installed and it goes directly inside the meter. In my case
the meter is on the utility pole and power then runs about 75 ft underground
to the house. I like having my first line of defense against Mother Nature
75 ft away from the house. I have had no lightning problems in the house
since I installed surge suppressors (Joslyns) in the two main breaker
panels and the utility installed one in the meter, even though there has
been at least one lightning hit on a power pole only 3 poles from my pole
with the transformer and meter.
But I did have a hit a few days ago on the yard light on the barn which took
out some wiring in a conduit. I have yet had any desire to test my band-
saw and cut-off saw which were plugged into the outlet that got smoked.
This lightning ignored my 170 ft tower which was well grounded and on top
of the hill and hit the barn which is down in a valley about 500 ft from
the tower and just outside the "cone-of-protection" from the towers. The
barn is on its own meter and I have yet to add any lightning protection to
that site. (Why, I ask, does it take a direct hit before I get around to
doing anything? HINT: Don't wait!)
My personal experiences with a number of hits are that well-grounded towers
with lots of grounded Yagi elements do tend to drain away the charge build-up
that provides a track for the stepped-leader pre-cursor of the main stroke.
My years in radio astronomy with big HF and VHF arrays on a mountain top
(8500ft) indicated that 90% of our damage was due to spikes coming in the
UNDERGROUND power lines. So don't assume that since your lines are
underground you don't need to do anything. The old constant voltage
transformers (Sola, etc.) that are ferro-resonant would not allow the fast
rise-time transients to get through. So all critical equipment (atomic
clocks, etc) were powered with voltage regulating transformers. (This was
before the days of MOVs and other surge suppressors.)
To give you an idea of how severe this site was, suffice it to say that the
building was a steel one mounted on a concrete slab and everything was well
grounded, but we even had occassions where we would have corona coming off
the pointed ends of the coat hangers hanging on the coat rack!
In these days I would (and have) take(n) advantage of any utility program that
will install surge suppression directly in the meter, then add my own
suppressors in the main breaker box, use power strips with surge suppression,
and put my own MOVs in any homebrew equipment and any commercial equipment
that didn't already have them. Total cost of all of this was less than the
cost of the Icom IC-781 repair after a lightning transient came up a 1500 ft
long control cable, through a non-protected power strip and into the 781 power
BTW The Rohn part numbers for the microwave-style double-guying big-triangle
bracket (the Torque Arm Stabilizer Assembly) are TA45 for Rohn 45 and
TA55 for Rohn 55. I highly recommend them at points of highest torque
loading such as at the top of the tower with a big Yagi or, in my case, at
the guy point at the rotator for "elevated rotator" rotating tower
installations. The equalizer plate in the photo on the Jan 94 CQ is home
Rotating towers by definition have no torque assistance from the guy
wires but with proper design (heavy enough tower and well balanced
antennas) can be done safely. I have one rotating 170 ft tower that has the
bearing and rotator at 40 ft and then 3 sets of slip rings at 80/120/160 ft.
Current antennas are 4L KLM 40M Yagis at 80 and 160 and 7L 15M Yagis on
48 ft booms at 40 and 120 ft. We often get winds of 60-70 mph and I have
never detected any oscillation in the tower inself. I went out during a
gust front yesterday (63 mph peak) just to watch the tower through the
blowing sand/dirt and saw the Yagis bouncing around but no tower movement.
75 KW TRANSMITTERS
To Steve, KO0U/4. Yes I did build those 75 KW (49 MHz) pulse transmitters
that you used in Hawaii. I originally built 74 of those for a big radar in
Alaska that used 64 of them, plus spares. They were gutless wonders in order
to keep the cost low. No real protection or monitoring circuitry but they
did put out a lot of power for an 8877 when running pulses of a few
microseconds each at duty cycles of up to 2%. After completing the
Alaska mission (10 years of service) those transmitters are scattered
all over the Pacific (and other places) for wind profiling research. I now
build a 4th generation version of that transmitter and now use 3CX5000s in a
design that uses a microprocessor for remote operation/monitoring.
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